A photographer tested the concentration of several pairs of dogs as he captured their reactions in a series of photos – enticing them with treats. (Photos: Vieler Photography/Caters News)

A photographer tested the concentration of several pairs of dogs as he captured their reactions to treat time in a series of shots.

Christian Vieler, 47, of Waltrop, Germany, has been a professional dog photographer since 2016. He came up with the idea of snapping two dogs catching treats simultaneously — and the outcome will have you howling.

The series of images, published in September 2017, show dogs including a pair of Labradors, two Border Collies and a couple of Basset Hounds as they hope to become the ultimate good boy.

“I tried to catch the faces of dogs while they are trying to catch a treat in midair, looking shocked, confused, joyful or sad,” Vieler said.